Purpose: Drawing on the self-protection model, this study examines how leader narcissism can unwittingly increase subordinates’ cheating via workplace uncertainty and explores the negative potential of job autonomy for such behavior. Design/methodology/approach: Two independent three-wave, time-lagged surveys were conducted in South Korea, including 209 subordinates (Study 1) and 151 supervisor-subordinate dyads (Study 2), with hypotheses tested via path analyses. Findings: Leader narcissism heightened employees’ uncertainty, increasing cheating likelihood. Job autonomy amplified this effect. Results were consistent across self- or other-rated leader narcissism. Practical implications: Organizations should mitigate uncertainty through leadership training, structured performance evaluations and balancing autonomy with accountability to limit cheating. Originality/value: This study advances understanding of the bright and dark sides of narcissistic leadership by showing how it can spur subordinates’ cheating behavior and highlights that job autonomy, typically considered beneficial, can facilitate misconduct under certain contexts.